A Modular 2-DOF Serial Robot Manipulator for Education in Robot Control

2016 ◽  
Author(s):  
Stephen Mascaro
Keyword(s):  
Robot Control ◽  
Inverse Dynamics ◽  
Position Control ◽  
Sliding Mode ◽  
Feedforward Control ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Force Sensor ◽  
Control Techniques ◽  
Serial Robot

This paper describes a modular 2-DOF serial robot manipulator and accompanying experiments that have been developed to introduce students to the fundamentals of robot control. The robot is designed to be safe and simple to use, and to have just enough complexity (in terms of nonlinear dynamics) that it can be used to showcase and compare the performance of a variety of textbook robot control techniques including computed torque feedforward control, inverse dynamics control, robust sliding-mode control, and adaptive control. These various motion control schemes can be easily implemented in joint space or operational space using a MATLAB/Simulink real-time interface. By adding a simple 2-DOF force sensor to the end-effector, the robot can also be used to showcase a variety of force control techniques including impedance control, admittance control, and hybrid force/position control. The 2-DOF robots can also be used in pairs to demonstrate control architectures for multi-arm coordination and master/slave teleoperation. This paper will describe the 2-DOF robot and control hardware/software, illustrate the spectrum of robot control methods that can be implemented, and show sample results from these experiments.

Educational Force Control Using a Modular 2-DOF Serial Robot Manipulator and Low-Cost 2-DOF Force Sensor

2019 ◽  
Author(s):  
Stephen Mascaro
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Hybrid Control ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Low Cost ◽  
Force Sensor ◽  
Physical Contact ◽  
Dynamic Force ◽  
Control Techniques

Abstract This paper describes a modular 2-DOF serial robotic system and accompanying experiments that have been developed to instruct robotics students in the fundamentals of dynamic force control. In prior work, we used this same robot to showcase and compare the performance of a variety of textbook techniques for dynamic motion control (i.e. fast/accurate trajectory tracking using dynamic model-based and robust control techniques). In this paper we now add a low-cost 3D-printed 2-DOF force sensor to this modular robot and demonstrate a variety of force control techniques for use when the robot is in physical contact with the environment. These include stiffness control, impedance control, admittance control, and hybrid position/force control. Each of these various force control schemes can be first simulated and then experimentally implemented using a MATLAB/Simulink real-time interface. The two-degrees of freedom are just enough to demonstrate how the manipulator Jacobian can be used to implement directional impedances in operational space, and to demonstrate how hybrid control can implement position and force control in different axes. This paper will describe the 2-DOF robot system including the custom force sensor, illustrate the various force control methods that can be implemented, and demonstrate sample results from these experiments.

Adaptive Sliding Mode Impedance Control of Single-Link Flexible Manipulators interacting with the Environment at an Unknown Intermediate Point

Robotica ◽  
2019 ◽  
Vol 38 (9) ◽  
pp. 1642-1664 ◽  
Author(s):  
Ali Fayazi ◽  
Naser Pariz ◽  
Ali Karimpour ◽  
V. Feliu-Batlle ◽  
S. Hassan HosseinNia
Keyword(s):  
Position Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Detection Algorithm ◽  
Reference Trajectory ◽  
Constrained Motion ◽  
Intermediate Point ◽  
Control Scheme ◽  
Single Link ◽  
Motion Mode

SUMMARYThis paper proposes an adaptive robust impedance control for a single-link flexible arm when it encounters an environment at an unknown intermediate point. First, the intermediate collision point is estimated using a collision detection algorithm. The controller, then, switches from free to constrained motion mode. In the unconstrained motion mode, the exerted force to environment is nearly zero. Thus, the reference trajectory is a prescribed desired trajectory in position control. In the constrained motion mode, the reference trajectory is determined by the desired target dynamic impedance. The simulation results demonstrate the efficiency of proposed control scheme.

A hybrid impedance control scheme for underwater welding robots with a passive foundation in the controller domain

SIMULATION ◽  
2017 ◽  
Vol 93 (7) ◽  
pp. 619-630 ◽  
Author(s):  
Sunil Kumar ◽  
Vikas Rastogi ◽  
Pardeep Gupta
Keyword(s):  
Minimum Distance ◽  
Position Control ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Graph Model ◽  
Proportional Integral Derivative ◽  
End Effector ◽  
Flexible Arm ◽  
Control Scheme ◽  
Effective Stability

A hybrid impedance control scheme for the force and position control of an end-effector is presented in this paper. The interaction of the end-effector is controlled using a passive foundation with compensation gain. For obtaining the steady state, a proportional–integral–derivative controller is tuned with an impedance controller. The hybrid impedance controller is implemented on a terrestrial (ground) single-arm robot manipulator. The modeling is done by creating a bond graph model and efficacy is substantiated through simulation results. Further, the hybrid impedance control scheme is applied on a two-link flexible arm underwater robot manipulator for welding applications. Underwater conditions, such as hydrodynamic forces, buoyancy forces, and other disturbances, are considered in the modeling. During interaction, the minimum distance from the virtual wall is maintained. A simulation study is carried out, which reveals some effective stability of the system.

Dynamic Analysis and Sliding Mode Impedance Control of a Robot Manipulator Subject to Impact/Contact With an Arbitrary Environment

2010 ◽  
Author(s):  
Masih Mahmoodi ◽  
Mehrdad Farid ◽  
Mohammad Eghtesad
Keyword(s):  
Abrupt Change ◽  
Sliding Mode ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Contact Dynamics ◽  
Simulation Studies ◽  
Environment Impact ◽  
Contact Phenomenon ◽  
Simulation Results ◽  
Contact Impact

In this paper, dynamic equations of a robot manipulator subject to compliant contact/impact with the environment are derived using nonlinear elastodynamic approach. Then, a sliding mode impedance algorithm is proposed to control compliant impact/contact dynamics of the robot manipulator with an arbitrary environment. Impact/contact phenomenon can be regarded as a perturbation due to an abrupt change of system’s velocity. Thus the need to have robust characteristics in such systems especially after impact seems to be evident. The performance of the proposed controller is compared against standard second order impedance controller through numerical simulation studies. Finally, simulation results are provided to show the effectiveness of the proposed algorithm.

Hybrid Position and Force Control Without Force Sensor

1996 ◽  
Vol 8 (3) ◽  
pp. 226-234
Author(s):  
Kiyoshi Ohishi ◽  
◽  
Masaru Miyazaki ◽  
Masahiro Fujita ◽  
Keyword(s):  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Hybrid Control ◽  
Robot Manipulator ◽  
Reaction Force ◽  
Force Sensor ◽  
Force Estimation ◽  
Estimation System ◽  
Dynamics Calculation ◽  
Torque Observer

Generally, hybrid control is realized by sensor signal feedback of position and force. However, some robot manipulators do not have a force sensor due to the environment. Moreover, a precise force sensor is very expensive. In order to overcome these problems, we propose the estimation system of reaction force without using a force sensor. This system consists of the torque observer and the inverse dynamics calculation. Using both this force estimation system and <I>H</I>∞ acceleration controller which is based on <I>H</I>∞ control theory, it takes into account the frequency characteristics of both sensor noise effect and disturbance rejection. The experimental results in this paper illustrate the fine hybrid control of the three tested degrees-of-freedom DD robot manipulator without force sensor.

Development and experimental evaluation of multi-fingered robot hand with adaptive impedance control for unknown environment grasping

Robotica ◽  
2014 ◽  
Vol 34 (5) ◽  
pp. 1168-1185 ◽  
Author(s):  
Ting Zhang ◽  
Li Jiang ◽  
Shaowei Fan ◽  
Xinyu Wu ◽  
Wei Feng
Keyword(s):  
Position Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Adaptive Estimation ◽  
Environmental Parameters ◽  
Parameters Estimation ◽  
Friction Compensation ◽  
Adaptive Sliding Mode ◽  
Force Tracking ◽  
Artificial Hand

SUMMARYThis paper presents adaptive impedance controllers with adaptive sliding mode friction compensation for anthropomorphic artificial hand. A five-fingered anthropomorphic artificial hand with multi-sensory and Field-Programmable Gate Arra (FPGA)-based control hardware and software architecture is designed to fulfill the requirements of the grasping force controller. In order to improve the force-tracking precision, the indirect adaptive algorithm was applied to estimate the parameters of the environment. The generalized momentum-based disturbance observer was applied to estimate the contact force from the torque sensor. Based on the sensors of the finger, an adaptive sliding mode friction compensation algorithm was utilized to improve the accuracy of the position control. The performances of the force-tracking impedance controller and position-based joint impedance control for the five-fingered anthropomorphic artificial hand are analyzed and compared in this paper. Furthermore, the performances of the force-tracking impedance controller with environmental parameters adaptive estimation and without environmental parameters estimation are analyzed and compared. Experimental results prove that accurate force-tracking and stable torque/force response under uncertain environments of unknown stiffness and position can be achieved with the proposed adaptive force-tracking impedance controller with friction compensation on five-finger artificial hand.

Dynamics and Trajectory Tracking Control of a Two-Link Robot Manipulator

2004 ◽  
Vol 10 (10) ◽  
pp. 1415-1440 ◽  
Author(s):  
Anthony Green ◽  
Jurek Z. Sasiadek
Keyword(s):  
Fuzzy Logic ◽  
Time Delay ◽  
Inverse Dynamics ◽  
Position Control ◽  
Robot Manipulator ◽  
Phase Response ◽  
Control Law ◽  
Minimum Phase ◽  
Linear Quadratic ◽  
Trajectory Tracking Control

Operational problems with robot manipulators in space relate to several factors, most importantly, structural flexibility and subsequent difficulties with their position control. In this paper we present control methods for endpoint tracking of a 12.6 × 12.6m2 trajectory by a two-link robot manipulator. Initially, a manipulator with rigid links is modeled using inverse dynamics, a linear quadratic regulator and fuzzy logic schemes actuated by a Jacobian transpose control law computed using dominant cantilever and pinned-pinned assumed mode frequencies. The inverse dynamics model is pursued further to study a manipulator with flexible links where nonlinear rigid-link dynamics are coupled with dominant assumed modes for cantilever and pinned-pinned beams. A time delay in the feedback control loop represents elastic wave travel time along the links to generate non-minimum phase response. A time delay acting on control commands ameliorates non-minimum phase response. Finally, a fuzzy logic system outputs a variable to adapt the control law in response to elastic deformation inputs. Results show greater endpoint position control accuracy using a flexible inverse dynamics robot model combined with a fuzzy logic adapted control law and time delays than could be obtained for the rigid dynamics models.

scholarly journals Robust position-based impedance control of lightweight single-link flexible robots interacting with the unknown environment via a fractional-order sliding mode controller

Robotica ◽  
2018 ◽  
Vol 36 (12) ◽  
pp. 1920-1942 ◽  
Author(s):  
Ali Fayazi ◽  
Naser Pariz ◽  
Ali Karimpour ◽  
Seyed Hassan Hosseinnia
Keyword(s):  
Fractional Order ◽  
Position Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Lyapunov Theory ◽  
Reference Trajectory ◽  
Constrained Motion ◽  
Unknown Environment ◽  
Control Scheme ◽  
Single Link

SUMMARYThis paper presents a fractional-order sliding mode control scheme equipped with a disturbance observer for robust impedance control of a single-link flexible robot arm when it comes into contact with an unknown environment. In this research, the impedance control problem is studied for both unconstrained and constrained maneuvers. The proposed control strategy is robust with respect to the changes of the environment parameters (such as stiffness and damping coefficient), the unknown Coulomb friction disturbances, payload, and viscous friction variations. The proposed control scheme is also valid for both unconstrained and constrained motions. Our novel approach automatically switches from the free to the constrained motion mode using a simple algorithm of contact detection. In this regard, an impedance control scheme is proposed with the inner loop position control. This means that in the free motion, the applied force to the environment is zero and the reference trajectory for the inner loop position control is the desired trajectory. However, in the constrained motion the reference trajectory for the inner loop is determined by the desired impedance dynamics. Stability of the closed loop control system is proved by Lyapunov theory. Several numerical simulations are carried out to indicate the capability and the effectiveness of the proposed control scheme.

scholarly journals Robust Control for a Two DOF Robot Manipulator

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Fatma Massaoudi ◽  
Dorsaf Elleuch ◽  
Tarak Damak
Keyword(s):  
Robust Control ◽  
Sliding Mode Control ◽  
Sliding Mode ◽  
Robot Manipulator ◽  
Model Uncertainties ◽  
Robot System ◽  
Control Techniques ◽  
Simulation Results ◽  
Manipulator Robot

In this paper, we present robust control techniques applied on a manipulator robot system: modified sliding mode control (MSMC) and backstepping control (BSC). The purpose is to evaluate SMC and BSC performances, taking into account the model uncertainties. Then, the obtained results of MSMC technique are compared with those of the adaptive sliding mode. Both methods have comparable simulation results which show a good quality of robustness. However, simulation results prove that the modified SMC is more robust, mostly under the effect of external variations and uncertainties.

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